Status Byte - Siemens SIMATIC S5 Manual

Integral Standard Function Blocks L2-SEND and L2-RECEIVE
5.4

Status Byte

The status byte (STB) is used to control the data transmission using L2-SEND and L2-RECEIVE.
You need to evaluate the status byte in order to monitor the data exchange between the control
processor of the S5-95U and the communications processor of the S5-95U. The status byte
indicates errors and the status of a job and informs you about data management.
Define the location of the status byte in DB1..
e.g., flag byte 200
Status byte (STB)
7 6 5 4
Explanations of
the error display:
see Table 5-8
Job completed
with error
Job completed
without error
Job in progress
Receive viable
(i.e., you can fetch
data with
L2-RECEIVE)
*
With FBs L2-RECEIVE, the flag byte immediately following the
status byte is reserved for the length byte.
It is not available to the user.
Warning
!
If you write in the status byte, undefined states can occur during job processing.
You may only read the status byte.
5-6
3 2 1 0 7
Indicates for FB L2-RECEIVE the quantity of data in bytes
( 1 to 242) that have been copied to the destination area
(without leading sign)
Figure 5-3. Structure of the Status Byte
e.g., flag byte 201
Length byte (LB)*
6 5 4 3 2
S5-95U, SINEC L2
1 0
EWA 4NEB 812 6112-02